I cannot flash the firmware

Please confirm there is no burnt component on the circuit. That situation would commonly happen if a very high current goes through the measurement circuit. If you find burnt parts on the circuit, please take a picture of the circuit and send it to us at support@tytorobotics.com for further troubleshooting.
Please confirm that you can get the COM port number from the GUI. You can try to plug and unplug the USB connector on the PC and look for a new COM port in the COM menu after connecting the USB to your computer.
Please check the green LED on the circuit and see whether it is on. If the green LED is ON, it means that circuit is powered properly.
If your problem is not solved after completing the steps above, please contact us with details on your problem, and we will try to help. Please attach the invoice you got when you purchased our products in the email you send to us.